Also (and the nuclear analogy is also apropos here) the big boys dont want simply to abolish software patents altogether, since they basically present huge barriers to entry that can be used against smaller upstart competitors. So it's only a zero-sum legal quagmire between the superpowers, but they can jointly maintain the status quo by threatening newcomers.
On the other hand, microsoft and the others are afraid of these productless patent holding companies (sort of like stateless nuclear terrorists) that can dish out lawsuits while having no products of their own liable to countersuit.